# Ventilation Mechanism > Part of: [Greenhouse Construction](/greenhouse-construction.md) · Provider: [DutchGreenhouses](/) The ventilation mechanism opens roof windows along both sides of the ridge, driven by rack-and-pinion or push-tube gear from a motor. It runs on wind and buoyancy rather than energy, so vent area sets the ceiling on how much heat a greenhouse sheds before active cooling is needed. ## Facts | Property | Value | |---|---| | Recommended ridge vent area | 15–20 % of floor area | | Running energy | 0 kWh per hour of ventilation | | Drive mechanism | Rack-and-pinion or push-tube mechanism | | Control inputs | 5 inputs | | Installation stage | Before steel erection sequence position | Structure # Ventilation mechanism. The first and cheapest climate tool: outside air. ## The first and cheapest climate tool: outside air Before any pump, boiler or cooling unit is switched on, a greenhouse has one climate tool that costs nothing to run: its windows. The ventilation mechanism is what opens the roof to the sky, exchanging the warm, humid air inside for cooler, drier air outside — dumping excess heat, releasing moisture and refreshing CO₂-depleted air all at once. Because it runs on wind and natural buoyancy rather than energy, ventilation is always the first line of climate control, and a greenhouse that ventilates well needs less of everything more expensive. Mechanically, the standard is a motor-driven push-pull system that opens roof windows along both sides of the ridge. Driving the rack-and-pinion or push-tube gear moves whole rows of ventilation lights together, and opening on both sides of the ridge lets the grower ventilate on the leeward side in high wind — shedding heat without letting a gale tear through the crop. The amount of ventilation area designed into the roof is one of the most important early decisions, because it sets the ceiling on how much heat the greenhouse can shed passively before active cooling is needed. Installation is woven into the construction sequence. The ventilation mechanism is mounted to the trusses before the steel is raised, while the work can be done safely and accurately at ground level, so that once the frame is up the roof is already able to open. This is also why the earlier structural stages leave provisions for it — the mechanism is planned in from the start, not retrofitted. In operation, the windows are not simply opened and closed but steered continuously by the climate computer. Window position is calculated against the inside climate, the wind speed and direction, rainfall and humidity, so each section opens exactly as far as conditions allow — wide open to shed heat on a calm warm day, eased back or switched to the leeward side as the wind rises, closed against driving rain. DutchGreenhouses® engineers the ventilation capacity and control into the structure from the outset. Get in touch to discuss your greenhouse. From the knowledge base ## Reads you might find interesting ceacultivationbusiness-case ### Grow Like a Pro: Starting Smart, Growing Strong How Grow Like a Pro combines smart farming, CEA technology and local partnerships for eco-friendly, profitable, pesticide-free greenhouse pr Read article education ### The Case for a College Greenhouse Why a college greenhouse belongs in the curriculum: teaching science, craftsmanship, business logic and sustainability, and preparing studen Read article education ### The Case for a High School Greenhouse Why every high school greenhouse matters: how it makes STEM tangible, builds responsibility and teamwork, and helps students discover their Read article education ### Greenhouses in Education: The Case for Schools Greenhouses in education reconnect students to reality — the full case for why every school, high school, college and trade program should h Read article historyconstruction ### The Origins of Greenhouse Horticulture: My Backyard A tour through greenhouse horticulture history: from 19th-century Westland fruit walls to the “City of Glass” and today’s international high Read article company ### DutchGreenhouses Rebranded: A New Corporate Identity Announcing our new corporate identity — a visual style reflecting our dedication to advanced, high-quality greenhouse projects and The Futur Read article ## FAQ **How much ventilation area does a greenhouse need?** ASAE guidance puts ridge and sidewall vent area as equal and each 15 to 20 percent of floor area, giving 30 to 40 percent combined. That combined figure is frequently misquoted as the total, which under-sizes the roof by half and pushes load onto active cooling that natural ventilation should have handled. **Why do windows open on both sides of the ridge?** To let the grower ventilate on the leeward side in high wind. Opening into the wind would drive a gale through the crop; opening away from it still sheds heat while the structure and the plants stay protected. The choice is made continuously by the climate computer from wind direction. **Is roof ventilation really free?** Close to it. Beyond the drive motors it consumes no energy, because it works on wind pressure and thermal buoyancy rather than fans. That is why it is the first climate tool a greenhouse uses: every kilowatt of heat shed through the roof is a kilowatt the cooling system does not have to remove. **What happens if insect netting is fitted over the vents?** Airflow drops, and the finer the mesh the larger the drop. The two systems have to be sized together: where a fine mesh is needed to exclude thrips, the ventilation area is increased to compensate, so the pest barrier does not quietly remove the cooling capacity the greenhouse was designed around. ## Related [Greenhouse Construction](/greenhouse-construction.md) · [Steel Structure](/greenhouse-construction/steel-structure.md) · [Aluminium System](/greenhouse-construction/aluminium-system.md) · [Roof Vent](/glossary/roof-vent.md) · [Rack-and-Pinion Mechanism](/glossary/rack-and-pinion.md) · [Climate Computer](/glossary/climate-computer.md)